Connecting device



Dec; 31, 1935. s. "r, CURRAN 2,026,303

CONNECTING DEVICE Filed Juh 9, 1934 s Sheets-Sheet 1 i we 'V ENTbR S. 7TCURRAN '%(a%/MQ( ATTORNEY s. T. CURRAN 2,026,303

CONNECTING DEVICE Filed June 9, 1934 3 Sheets-Sheet 2 A INVEN TOR S. 7'. CUR/PAN 4 TTORNEV Dec. 31, 1935.

Dec. 31", 1935. 5 1- CURRAN 2,026,303

' CONNECTING DEVICE i Filed June 9, 1934 3 Sheets-Sheet 3 CONDENSER PLUG //v l/E/VTOR S. 7? CURRAN' ATTORNEY Patented Dec. 31

PATENT OFFIGE CONNECTING DEV'IGE' Stanley T. Gurran,.Mountain Lakes, N. J., as-

signor ween Telephone Laboratories, Incorporated; New York, N. Y., a corporation of New York Applicationdune 9,1934, Serial No. 729,731

This' invention relates to a connecting device and more particularly to a'combinedmulti-com tact plug andkeyset.

The object of thisinventiorr is to connect the contacts of a-rnulti-contact electrical elementtor a testing system.

A feature of this invention resides ina setof' springv pressed plunger contactsto engage the contacts of an electrical. element.

Another feature" resides in spring clamping members forh'olding the connectingdevice to the element engaged'by the contacts.

Another feature resides in a setof manually operated keys and associated contact springs laithrough which connections maybe selected and extending from plunger contactsin the device to a testing system.

Still another feature resides in strap connection members which form electrical connections between common sides of the contact springs in the keyset.

In the drawings, Fig. 1 is'a view in'perspective of the connecting deviceanda multi-unit condenser;

Fig. 2 is aside elevational view partly. in section of the connecting device;

Fig. 3 is a bottom plan View partlyiin section of the connecting device;

Fig. 4 is an end viewtaken from the left'end" of the device shown in Fig. 3;

Fig. 5 is an end view partly in section of the. device taken from the rightend of the device. shown in Fig. 3 and sectioned to the broken line Fig. 6 is a schematic view-of thedevice connected to atesting system; 7

Fig. 7 shows views in perspective and partly in section'of details of the deviceythe parts being shown in partly assembled condition;

Fig. Sis an exploded view showing'in perspective, strap connection members for common sides of spring contacts of the keyset; and

Fig. 9 is a-schematic showing the: circuit arrangement of the device-connected to a multi-unit 45 condenser.

In making capacitance-tests-of circuits including condensers it is desirable that some means be provided for readily bringing the portion of the circuit to be tested into connection with suitable testing apparatus.

To eifect economies inthe electrical artin the manufacture of fixed condensers, it has been found advisable to make multi-unit condensers instead of making a large number of individual fixed condensers of difierent' values; These multi-unit condensers are provided with a plu-' rality of terminals which may be selectivelyconnected to conductors of a circuit or may be con nected-together by suitable conductive straps to obtain the required capacitance value. When a multi-unit condenser has been placed in the circuit and a required capacitance value has been obtained by connecting into the circuit selected portions ofthe condenser, certain terminals of the multi-unit condenser are connected by strap'con-- ductorsto make the selected portions'of the condenser a permanent part of the'circuit.

Where a comparatively large number of con densers of a certain predetermined value are in constant demand, it is frequently found desirable to carry a stock of condensers of the required value. The condensers placed in stock for this purpose may be multi-unit condensers in which' certain predeterminedterminals have been strapconnected to set the condensers at the required value. In-making these condensers and determining which of the terminals should be con nected by strap conductors, it is desirable that some means he provided for connecting suitable testing apparatus to a multi-unit condenser and for selectively connecting the various units of the condenser to the testing apparatus.

I have found in making certain tests of electri-- cal systems and apparatus units that if comparatively long conductors are employed in extending; connections from the system or apparatus under test, to testing apparatus that undesirable values of resistance or capacitance or both are introduced which affect the testing apparatus and prevent the apparatus from giving a true indication of the electrical value of a system or apparatusunit under test. For instance, if comparatively long conductors are employed in extending connections from' terminals of a condenser to testing apparatus and the long conductors extend parallel to each other, a certain capacitance value inherent in the long conductors will be included in the results shown or-indicated by the testing apparatus. To determine the true electrical value of a system or apparatus unitunder test as it will be when the long conductors are removed, the value introduced by the long conductors must be calculated and deducted'from the reading given by the testing. apparatus.

The device of this invention serves as a means for connecting a multi-unit condenser to testing. apparatus and for selectively bringing the various units of the condenser into circuit connection with the testing apparatus to determine what portion or portions of the multi-unit condenser are required to obtain the required capacitance value. In this device no comparatively long conductors are employed in extending connections from the terminals of a system or apparatus unit to the testing apparatus. The device of this invention is brought into direct contact with the terminals of a system or apparatus unit under test and terminals are provided on the device to facilitate connection of the device to a testing system. With this device the possibilities of introduction of undesirable electrical values between the system or apparatus unit under test and'the testing apparatus are reduced to a minimum.

In Fig. 1 a typical multi-unit condenser II is shown comprising a rectangular metal can I2 which contains the various layers of conducting and non-conducting material employed in a well known manner in fixed condensers of this type. A pair of terminals I3 and I4 to be connected to conductors of a circuit extend from one end of the condenser and a group of terminals I5 which serve as terminals for the various condenser units enclosed in the can project outward from the end of the condenser II opposite to that from which the terminals I3 and I4 project. In the group of terminals I5 there are twelve terminals which in practice may or may not bear identifying numbers or figures but which for the purpose of illustration we will assume to be numbered and lettered respectively in the order in which they stand as 1, 2, 3, 4, A, 5, 6, C, 7, 8, 9 and 10. Around each end of the cam I2 are metal beads I6 and I1 formed by overlapping edge portions of the ends of the can.

The connecting device of this invention which for the purpose of identification has been given the general number I8 is shown to the right of the condenser II in Fig. 1. In the connecting device I8 a substantially rectangular hollow shell I9 is formed by an upper half 23 and a lower half 2I. These upper and lower halves 20 and 2 I respectively, are substantially rectangular channel members which may be made of metal or insulating material. The two halves 28 and 2| of the'hollow shell I9 are held in cooperating relation to form a casing by means of spaced insulating blocks 22 and 23, shown in Figs. 2 and 3, and by other parts which will be subsequently described, all located within the shell I9 and by the machine screws 24. The upper and lower halves 20 and 2I, respectively of the hollow shell I9 are widened at the right ends as shown in Figs. 1 and 3 and the channels are reduced in depth at these points as shown in Figs. 1 and 2 to form a housing portion 25 for key contacts 26. The key contacts 26 are manually operated by means of cams 27 which project through spaced apertures in an apertured panel 23 which is disposed across an elongated aperture 29 in the key housing portion 25 of the shell I9. The cams 2'I are substantially circular blocks of insulating material which may be, for instance, a hard rubber composition or bakelite. A fiat portion is provided on the periphery of the cams 27 at 32 as shown in Fig. 2 to permit separation of the key contacts 26. A radially extending portion 3i is also provided on the periphery of each cam 21. This radially extending portion 3I is knurled on the outer edge to enable an operator to manually rotate the cam. Extending laterally through substantially the center of each cam 27 is a pin 32. The pin 32 projects a sufficient distance beyond the sides of the cam to form trunnions for the cam and is knurled at the center and drivefitted to the cam so that it will rotate with the cam. The keys comprising the cams 2? and the key contacts 26 are divided into two groups to permit reduction in the width of the key housing 5 portion 25 of the connecting device I8. The keys, however, could be arranged all in a single line and the cams could be arranged so that they would all project through either the upper or the lower face of the key housing portion 25 of the connecting device I8. For the purpose of illustrating this invention, however, it will be assumed that the keys are divided into two groups and that they are arranged as shown in Figs. 1, 2, 3 and 5 of the drawings. In the structure shown there are six keys in the upper half 25 of the device and five keys in the lower half 2 I. All of the cams 27 are not shown in Fig. 5 since in some parts the section line 5-5 runs back of the cams 21. The cams 21 for operating the key contacts 26 in the upper half 20 of the shell, project through spaced apertures in the apertured panel 28. The cams 21 for operating the key contacts 26 in the lower half of the shell project through spaced apertures in an apertured panel 28 in the lower half 2I of the shell. To support the cams 2'I in the upper half 20 of the shell, a substantially rectangular fiat plate 33 shown in Figs. 2, 5 and 7 is secured by means of the screws 34 to the inner face of the upper half 28 of the shell I9 in the key housing portion 25. The plate 33 is provided with internally threaded spaced apertures 35 to receive the screws 3-2 and has rectangular spaced apertures 35 registering with the apertures in the apertured panel 28 35 located in the upper half 23 of the shell I9 to accommodate the cams 21. The apertured panel 28 is secured to the upper face of the plate 33 in the elongated aperture 29 of the upper half 23 of the shell I9 by machine screws 3'1, shown in Fig. 3, and one of which is shown in dotted line in Fig. 2. Extending laterally across the plate member 33 and in line with the lateral centers of the apertures 33 is a broken indentation 38 which faces the inner wall surface of the upper half 23 of the shell Ill. The indentation 38 in the plate member 33 serves as a rest for the projecting ends of the pins 32 of the cams2l. The projecting ends of the pins 32 of the cams 27 are trunnioned in the indentation 38 of the plate memher 33 and are held by the plate member 33 against the inner wall surface of the upper half 23 of the shell I9.

The cams 2? provided for operation of the key contacts 26 in the lower half 2i of the shell I9 are held in place by a rectangular plate 39 which corresponds to the plate 33 in the upper half 28 of the shell I9 except that the plate 39 has five spaced apertures for the cams 27. The indentation 38 extends only far enough across the plate to take care of five cams and in one end of the plate spaced apertures are provided to accommodate two binding posts A and C. The two plates 33 and 39 which serve to support the earns 22'? in addition to being secured to their respective upper and lower halves 29 and M of the shell III by means of the screws 34, are still further maintained in spaced relation by means of a pair of spaced metal blocks 25 located in the shell I9 and which are secured at one end by rivets M to a closed end 52 of the upper half 23 of the shell I9. The blocks 23 are provided with internally threaded apertures to receive machine screws 33 which pass through apertures in the closed end 44 of the lower half 2| of shell I9. The blocks 40 serve as restsand spacer'members for the free ends of the plates 33 and 39. The blocks 40 also serve to hold together the closed ends 42 and 44 of the respective halves 20 and 2| of the shell l9.

The key contacts 26 are paired spring finger members of conducting material. Each pair comprises an outer spring member 45 and an inner spring member 45. The outer spring member 45 has a straight apertured inner end portion to permit securement of the spring member 45 in a spring pile-up 41, an inwardly directed arm portion 48 and a substantially straight free end portion 49 bearing on its inner surface a contact point 50.' The inner spring member 46 of key contacts 26 is a straight spring finger member having suitable apertures near its inner end portion to permit mounting in the spring pile-up 41 and a contact 5| at its free end facing the contact point5fl of the outer spring member 45. Each pair of key contacts 25 is arranged in a separate spring pile-up 41. The spring pile-ups 41 for the upper row of keys are supported on the inner surface of the apertured plate 33 by means of machine screws 52 but by reason of insulating sleeves 53 and apertured insulating blocks 54 have no electrical connection with the apertured plate 33. The spring pile-ups 41 for the lower row of keys are supported by means of machine screws 52 on the inner surface of the apertured plate 39 and are insulated from the apertured plate 39 in the same manner as the spring pileups 41 in the upper row of keys are insulated. from the apertured plate 33.

A comparatively long rectangular metal plate 55 shown in Figs. 7 and 8 having spaced apertures 55 to accommodate the machine screws 52 and insulating sleeve 53 is provided as a common connection for the outer spring members 45 of the spring contacts for the upper row of keys. A comparatively long rectangular metal plate 51 shown in Figs. 7 and 8 having spaced apertures 55 similar to the metal plate 55 and having a comparatively large aperture 65 on one end to accommodate the shank of the binding post A is provided as a common connection for the outer spring members 45 of the spring contacts for the lower row of keys. Themetal plates 55 and 51, as shown in Figs. 5 and 7, are electrically connected on one end by means of a metal strap 58, shown in Figs. 5, 7 and 8 and are electrically connected on the other end by means of a metal strap 59, shown in the same figures. The metal strap 58 is laterally creased and outwardly bowed at 6|! from the ends of plates 55 and 51 and has spaced tabs 5| on its ends which are inserted through notches 62 in the ends of the plates 55 and 51 and bent over to secure the metal strap 58 to the ends of the plates 55 and 51. The metal strap 59 is similar to the metal strap 58 in that it is outwardly bowed from the ends of the plates 55 and 51 and has spaced tabs 63 on one end which pass through notches 64 in the adjacent end of the metal plate 55 and which are bent over to secure the strap 59 to the plate 55. The lower end of the metal strap 59, however, terminates in an inwardly directed end piece 55. The end piece 65 is apertured at B6 to receive the shank of binding post A. The binding post A is in electrical connection with the metal strap 59 and in cooperation with a nut 51 clamps the end piece 65 to the apertured metal plate 51. Each spring pile-up 41 for the upper row of keys and assuming that the beginning is at the top in Figs. 2-and 7 and at the right in Fig. 5 contains'the followingelements: An apertured block 54 of insulating material, the apertured inner end of the outer spring 45, the apertured metal plate 55, a comparatively narrow apertured strip of insulating material 68, a comparatively wide and apertured block of insulating material 59, an apertured inner end of the inner spring 46, an apertured block of insulating material 15, and a comparatively narrow apertured strip of insulating material 1|. Each spring pile-up 41 for the lower row of keys contains the same elements as those listed for the upper row with the exception that in the lower row the metal plate 51 takes the place of the plate 55 in the upper row. The inner end of each of the inner spring members 46, as shown in Figs. 2 and 3, is extended inward of the connecting device and beyond the pile-up 41 of conducting and insulating members above described and is apertured at 12 to permit attachment thereto of a conductor 13 leading to a plunger type contact to be subsequently described.

Within the shell 15 and supported by the spaced apertured insulating blocks 22 and 23 is a group of terminals 14 shown in Figs. 2, 3, 4 and '1. The number of terminals in the group 14 and the spacing and arrangement of the terminals correspond to the number and the spacing and arrangement of the group of terminals l5 which project from one end of the multi-unit condenser ll. Each terminal in the group 14 in the connecting device l8 as shown in Figs. 3 and 7 comprises a sleeve member 15 terminating in an externally threaded shank portion 15, a spring pressed plunger 11 operating within the sleeve 15 and a helical spring 18 within the sleeve 15 to continually urge the plunger 11 outward-oi the sleeve 15. The threaded shank portions of the terminals 14 are inserted in apertures in the insulating block 23 and project from the block 23 inward of the connecting device l8 toward the keys 25. A group of comparatively short insulated'oonductors 13 are provided within the connecting device E8 to form connections betweenthe group of terminals 14 and the inner spring members 45 of the keys 25. The sleeves 15 and the spring pressed plungers 11 of the group of terminals 14 are inserted in apertures in the insulating block 22 with the outer ends of the plungers 11 extending almost to the outer face of the insulating block 22. On the. outer end of each plunger 11 is an enlargement 15 having a concave outer face to engage a terminal in the group i5 of the multi-unit condenser ll.

Disposed about midway of the shank portion of the plunger 11 is an annular shoulder 85 of about the same diameter as the inside diameter of the sleeve 15. The outer end of the sleeve 15 is spun over the outer face of the annular shoulder to prevent complete removal of the plunger 11 from the sleeve 15. The sleeve 15 is supported on the inner end by an annular shoulder 8| which is integral with the shank 16. The helical spring 18 in the sleeve 15 and which continually urges the plunger 11 outward of the sleeve 15 is disposed around the inner end of the plunger between the inner face of the annular shoulder 80 of the plunger 11 and the inner end of the shank 15.

To hold this connecting device to an end of a multi-unit condenser spring latch members 82- 82 are provided. The spring latch members 8282 are provided with manually operated release buttons 83-83 which extend outward of the halves 20 and 2| of the shell l9 through apertures provided in the halves 25 and 2 I. In each half 20 and 2| a spring latch 82 is located. Each spring latch 82 as shown inthe upper. portionof Fig. 2

and still more clearly in Fig. '7 comprises a substantially long flat spring 84 terminating in one end in an enlarged portion 85 having an inwardly directed hook 86 and at the other end in an inwardly projecting end portion 81 to which is attached by means of screws 88 the manually operated release button 83. The enlarged portion 85 of each spring latch 82 is outwardly ofiset at 89 from the main portion of the spring latch and extends into apertures 9i] provided in the halves 25 and 2| of the shell I9. The aperture 90 in each half 25! and ZI-of the shell I9 permits outward displacement of the wide portion 85 of the spring latch 82 when the inwardly directed hook at is brought into engagement with the bead I6 of the condenser I I. The aperture 90 also permits outward movement of the large end 85 of the spring latch 82 by depression of the manually operated button 83 to release the hooked end 86 from engagement with the bead I6 of the condenser II when the connecting device-I8 is to be released from the condenser. To support the spring latch 82 and to provide the required spring tension for its operation, the latch 82 is attached to a free end of a substantially long leaf spring 9|. The leaf spring 9| projects from and is integral with a metal bracket 92. The metal'bracket 92 on its outer end is L-shaped in cross-section and is attached on one of its sides by means of screws 93 to the spaced insulating blocks 22 and 23. The screws 24 which enter the spaced insulating blocks 22 and 23 and which serve to hold the halves 2G and 2| of the shell I9 together also pass through apertures 94 in the metal bracket 92 and clamp the one side of the metal bracket 92 between the inner wall surfaces of the halves 25 and 2| and the spaced insulating blocks 22 and 23. The leaf spring 9| is substantially the same width as the narrow portion of the latch 82 and extends substantially parallel to the straight central portion of the latch 82. The lach 82 is secured by spaced bolts 95 to the free end of the leaf spring 9|. The latch 82 as shown in Fig. 2 is held against the inner wall surface of the upper portion of the upper half 20 of the shell IS. The point of attachment of the leaf spring 9| to the latch 82, namely, the point at which the leaf spring 9| is attached to the latch 82 by means of the bolts 95-95, forms a fulcrum for the latch 82. A duplicate of the latch 82 and the leaf spring 9|, shown in the upper section of Fig. 2, is provided in the lower portion of the casing I9. The leaf spring 9| in the lower portion is attached to a metal bracket 96 which is a duplicate of the metal bracket 92. The metal bracket 95 extends around the two sides of the spaced insulating blocks 22 and 23 not occupied by the metal bracket 92 and is attached to the spaced insulating blocks 22 and 23 and to the halves 20 and 2| of the shell I9 by screws 93 and 24, respectively. The positions of the metal brackets 92 and 96 relative to the insulating block 22 in shell I9 are shown in Fig. 4.

The connecting device I8 is provided with binding posts A and. C to permit attachment of the connecting device I 3 to testing apparatus such, for instance, as the testing apparatus 91 shown in Fig. 6. The testing apparatus 91 shown in Fig. 6 includes a bridge circuit 98, a source of current supply 99 and a galvanometer loll. When the connecting device I8 is to be brought into connection with the multi-unit condenser I I, the connecting device I3 is pushed against the group terminal end of the condenser I until the terminals of the group I5 come in contact with the concave outer faces of the enlargements 19 of the plungers TI. The connecting device I8 is then further thrust against the group terminals of the condenser until the hooked ends 86 of the latch springs 82 come in contact with the bead I6 of the condenser I I and pass over the bead I6. This last thrusting movement will cause pressing in-- ward of the plungers i1 and compression of the springs I8. The spring pressure therefore built up in the springs I8 will continually urge the plungers 11 against the terminals of the group I5 of the condenser I I and Will maintain the terminal plungers of the connecting device in good contacting relation with the group of terminals I5 of the condenser II. The latch springs 82 will hook against the inner surface of the bead l6 of the condenser I I and will prevent accidental dislodgment of the connecting device I8 from the condenser II. The circuit connections then established between the connecting device I8 and L the condenser II will be as shown in Fig. 9, the portion above the horizontal line being the multiunit condenser II and the portion below the line being the connecting device I8. The circles below the line marked with the letters and numerals from A to II] inclusive, represent the earns 27 of the connecting device I8. The circles above the line marked with the letters and numerals A to C inclusive, represent the group of terminals I5 of the multi-unit condenser II.

Assuming that the binding posts A and C are connected to the testing system 91 as shown in Fig. 6, and that cam I is operated to close outer spring contact 45 against the inner spring contact 46, the condenser unit associated with terminal I, shown in Fig. 9, will be bridged across the conducting leads from the binding posts A and C. Since as shown in Fig. 6 the binding posts A and C are connected in one arm of the bridge circuit 98 of the testing apparatus 91, the condenser unit associated with terminal I will be connected to the bridge circuit 98. It will be seen that by selectively operating the cams I to I0, inclusive, of the connecting device I8, the different units in the multi-unit condenser I I may be connected either singly or in various combinations in one of the arms of the bridge circuit 98 and that various units or combinations may be connected to the bridge circuit until the galvanometer I00 indicates that the required capacitance value is obtained. By noting the cams operated to obtain the required capacitance value and by permanently connecting the terminals in the group I5 associated with the unit or units required with the terminal A of the multi-unit condenser, the multi-unit condenser II may be set for a required capacitance value. For instance, terminal I may be strap-connected by a conducting lead to terminal A. If the condenser I is then connected to wires of a circuit through the terminals l3 and I4, the capacitance value of the unit associated with terminal I will be included in that circuit. If the terminals I, 2 and 3 are strapconnected to terminal A, the condenser units associated with terminals I, 2 and 3 will be connected in parallel across that portion of the circuit including the terminals 53 and I4. A numbered and lettered plate |8| bearing numbers and letters corresponding to the numbers and letters assigned to the group of terminals |5 of the condenser I I is secured in a depressed portion in the upper half 20 of the shell I9. Corresponding numbers and letters are also stamped on the cam portion end 25 of the connector I8 as shown at I 52 in Figs. 1 and 5. The numbers and letters at I02 are directly in line with the cams 21 and identify the contacts afiected by operation of each cam. By observing the cams operated and the numbers associated therewith and by noting the positions of the correspondingly numbered terminals as shown on the plate lfll, the terminals in the group I5 of the condenser unit to be strapconnected to the terminal A in that group may be readily determined.

To release the connecting device [8 from a condenser, the push-buttons 8383 are manually pressed toward each other to move the hook portions 86 of the latch springs 8282 out of engagement with the bead l 6 of the condenser l I. When the latch springs are released from engagement with the bead I6 of the condenser II, the spring pressure in the springs 18 of the terminals 14 will press the connecting device I8 outward of the multi-unit condenser H a sufiicient distance to move the hook portions 36 of the latch springs 82 outward past the bead l6 of the condenser II.

If a multi-unit condenser II is already connected in a circuit by having the terminals [3 and I4 connected to wires of the circuit and it is desired to adjust the multi-unit condenser to a required capacity value, a test with the condenser in circuit may be made by means of the connecting device [8 and suitable testing apparatus connected therewith. Assuming that a multiunit condenser is connected to the circuit wires of a system by way of the terminals l3 and I4 and that the connecting device [8 having the binding posts A and C connected to a testing system 91 is connected to the group of terminals 15 of the multi-unit condenser II and that the latches 82 are holding the connecting device l8 to the multi-unit condenser II, it will be seen by referring to Fig. 9 that by operating cam A to close the spring contacts 45-46 a connection is completed from terminal l3 to the binding post A and that none of the condenser units of the multi-unit condenser are connected to the testing apparatus 91 shown in Fig. 6. It is obvious that with this condition certain tests may be made of the system to which the terminals [3 and I4 are connected without having capacitance Values of any of the units of the multi-unit condenser ll affecting the system or the testing apparatus. By leaving cam A operated and by selectively operating the cams I to ID to close the spring contacts 45 and 46 associated with these cams, various capacitance values residing in the units of the multi-unit condenser may be selectively bridged across the line wires of the system under test. When the testing apparatus indicates that the required capacitance value has been introduced into the system under test, the

cams 21 standing in operated position will indicate which unit or units of the multi-unit condenser l I should be included in the system under test. To permanently set the multi-unit condenser to the required value, the terminal or ter- 5 minals in the group [5 corresponding. to the cam or cams operated is or are connected to the terminal A in the group 15 by a conductor, not shown, but which may, for instance, be a comparatively short lead wire soldered to the ter- 10 minals required.

What is claimed is:

1. A connecting device comprising an apertured hollow casing, a set of spaced spring pressed contacts in one end of said casing, a set of manually operated keys including cams supported in said casing, a pair of spaced leaf spring contacts for each of said keys, conductors connecting one of each pair of leaf spring contacts to one of said spaced spring pressed contacts, and a pair of manually operated resilient latch fingers supported in said casing, said resilient latch fingers having hooked ends operating in apertures in the casing to engage an electrical device and hold. the connecting device in engagement with the electrical device.

2. A connecting device comprising an apertured hollow casing having an open end portion and a closed end portion, a set of spaced spring pressed contacts in said open end portion extending longitudinally of said casing, paired key contacts in said closed end portion, manually operated cams supported in said casing and having portions projecting outward of said casing for manual operation and portions projecting inward of said casing to operate said key contacts, a pair of manually operated resiliently supported latch fingers supported Within said casing, operating buttons attached to said latch fingers, said operating buttons extending outward through apertures in said casing, individual spring supports within said casing for each latch finger, and means for connecting wires of a circuit to said connecting device.

3. A connecting device comprising a combined multi-contact plug and a set of manually openated keys, said keys having associated therewith paired spring contacts divided into two groups, conducting bars connecting one of the spring contacts of each pair to the like spring contact of the other pairs in that group and outwardly bowed flat spring straps connecting the flat bar of one group to the fiat bar of another and forming a common connection between the fiat bar connected contacts in each group.

STANLEY T. CURRAN. 

